Composite high-temperature valve and method of making the same

ABSTRACT

A valve head blank consisting of a briquette of water-atomized high-temperature-resistant metal powder, commonly called &#39;&#39;&#39;&#39;superalloy powder&#39;&#39;&#39;&#39; (FIGS. 1 to 5 inclusive) is compressed by the upper punch of a briquetting press in the cavity of a die containing a core rod to form a socket in the head, which is then sintered in a sintering furnace in a protective atmosphere at about 2,000* F. Meanwhile, a valve stem of ordinary steel has been cold-headed or machined at its upper end to form a slightly flared reduced-diameter nose thereon. This valve stem is placed in the die cavity of a press with its flared nose projecting upward into the die cavity. A trumpet-shaped lubricant sleeve of nonferrous metal, such a copper, is then placed in the die cavity, followed by the reheated sintered valve head with its socket telescoping with the flared nose of the valve stem. The upper punch of the press is then caused to compress and thin the valve head while at the same time to elongate and interlock the neck thereof with the flared nose of the valve stem by an extrusion action as the metal lubricant sleeve facilitates the deformation of the respective parts. Alternatively (FIGS. 6 to 9 inclusive), gas-atomized superalloy powder is molded into a valve head blank consisting of a preform in a mold also containing a core pin, this assembly being sintered in a sintering furnace as before. A flared-nose valve stem is again placed in the die cavity, followed by the lubricant metal sleeve and not sintered preform, whereupon the hot-forming, extruding and elongating operation is carried out as before.

United States Patent [72] Inventor John IIalier Northvilie, Mich. 121] Appl. No. 782,651 [22] Filed Dec. 10, 1968 [45] Patented June 8, I971 [73 1 Assignee Federal-Mogul Corporation Southfield, Mich.

[54] COMPOSITE HIGH-TEMPERATURE VALVE AND METHOD OF MAKING THE SAME 3 Claims, 10 Drawing Figs.

Primary Examiner-Samuel Scott Attorney-Barthel & Bugbee ABSTRACT: A valve head blank consisting of a briquette of water-atomized high-temperature-resistant metal powder, commonly called superalloy powder" (FIGS. 1 to 5 inclusive) is compressed by the upper punch of a briquetting press in the cavity of a die containing a core rod to form a socket in the head, which is then sintered in a sintering furnace in a protective atmosphere at about 2,000 F. Meanwhile, a valve stem of ordinary steel has been cold-headed or machined at its upper end to form a slightly flared reduced-diameter nose thereon. This valve stem is placed in the die cavity of a press with its flared nose projecting upward into the die cavity. A trumpet-shaped lubricant sleeve of nonferrous metal, such a copper, is then placed in the die cavity, followed by the reheated sintered valve head with its socket telescoping with the flared nose of the valve stem. The upper punch of the press is then caused to compress and thin the valve head while at the same time to elongate and interlock the neck thereof with the flared nose of the valve stem by an extrusion action as the metal lubricant sleeve facilitates the deformation of the respective parts.

Alternatively (FIGS. 6 to 9 inclusive), gas-atomized superalloy powder is molded into a valve head blank consisting of a preform in a mold also containing a core pin, this assembly being sintered in a sintering furnace as before. A flared-nose valve stem is again placed in the die cavity, followed by the lubricant metal sleeve and not sintered preform, whereupon the hot-forming, extruding and elongating operation is carried out as before.

PATENT-Emu 8l97| 3583672 SHEET 1 OF 2 INVENTOR JOHN HALLER ATTORNEYS PATENTEU JUN 8 :sn

SHEET 2 BF 2 FIG.9

INVENTOR JOHN HALLER BY HOJMQ" ATTORNEYS COMPOSITE HIGH-TEMPERATURE VALVE AND METHOD OF MAKING THE SAME In the drawings:

FIG. I is a central vertical section through the die cavity ofa briquetting press showing the formation of a valve head briquette from water-atomized superalloy powder, according to the invention, with the parts shown in the positions they occupy at the end of the briquetting stroke;

FIG. 2 is a side elevation on a reduced scale ofa multiplicity of valve head briquettes upon a ceramic block ready for insertion in the sintering furnace;

FIG. 3 is a central vertical section through the die cavity of a press with the component parts of the valve inserted in the die cavity, ready for the start of the compression stroke;

FIG. 4 is a view similar to FIG. 3, but showing the relative positions and proportions of the parts at the completion of the pressing stroke;

FIG. 5 is a side elevation of the trumpet-shaped nonferrous lubricant sleeve used in the pressing operation of FIGS. 3 and 4 and also of FIGS. 8 and 9;

FIG. 6 is a perspective view, upon a reduced scale, of a multiple cavity mold for' molding valve head preforms from gasatomized superalloy powder;

FIG. 7 is an enlarged vertical section through one of the mold cavities of FIG. 6, taken along the line 7-7 therein;

FIG. 8 is a central vertical section through the die cavity ofa press with the component parts of the valve of FIG. 7 inserted in the die cavity, ready for the start of the compression stroke; pp FIG. 9 is a view similar to FIG. 8 but showing the relative positions and proportions of the parts at he completion of the pressing stroke; and

FIG. 10 is a side elevation, upon a reduced scale, of the completed composite valve after grinding and finishing. Referring to the drawings in detail, FIGS. 1 to 5 inclusive illustrate the formation of a composite high-temperature-resistant valve, generally designated 10, shown in FIG. 10, using socalled water-atomized superalloy powder, the particles of which are or irregular shape so that they interlock and can therefore be compacted. Superalloys are so-called in the metal industries as being of a high chromium and cobalt content, with tungsten and nickel components in smaller proportions and with still smaller porportions of iron, silicon, manganese and carbon. They are distinguished for their considerably higher melting point than the carbon steels of which valve shanks are ordinarily made and for their resistance to hightemperature deformation or surface attack and certain of these superalloys have long been known by the name ofStellite and by the trade designations X-40" and HS 31." The water-atomization process is well known to those skilled in this art and is not a part of the present invention. Superalloys, however, are very expensive and ordinarily are prohibitively so for forming entire valves. The present invention provides a composite valve 10 of which the head 12 is of superalloy material and the stem 14 of ordinary inexpensive steel, while the neck of the head 12 is coated with a layer 18 of nonferrous lubricant metal such as copper, formed as a result of the process of the present invention.

The first step in the production of the head 12 of the valve 10 from water-atomized superalloy powder is to make a valve head blank consisting of a briquette 20 (FIGS. 2 and 3). The briquette 20 is made in a briquetting die 22 containing a substantially cylindrical die cavity 24 which is provided with an approximately shallow conical bottom surface 26 continuing downward in a sharply tapered conical surface 28 to a reduced diameter cylindrical bore 30 coaxial with the upper cylindrical portion 32 of the die cavity 24. The die 22 is mounted in a conventional briquetting press (not shown) provided with upper and lower punches 34 and 36 respectively which telescope with the cylindrical portion 32 of the die cavity 24 and with the lower cylindrical bore 30 of the die 22. The lower punch 36 is tubular, containing a cylindrical bore 38 in which is mounted a snugly fitting core rod 40. The core rod 40 projects upward into the die cavity 24 with its top slightly below the lower end of the cylindrical portion 32 thereof. The upper punch 34 at its lower end 42 is provided with a central convex protuberance 44 for shaping the top ofthe briquette 20.

At the start of the formation of the briquette 20, the upper punch 34 is raised completely out of the die cavity 24 while the remainder of the parts remain as shown in FIG. 1, namely the lower punch 36 and core rod 40. The die cavity 24 is then filled with the water-atomized superalloy powder. The upper punch 34 is now caused to descend upon a compression stroke, compressing the charge of superalloy powder into the shape of the preform 20 shown in FIG. 1, under a pressure of approximately 32 tons per square inch, while the protuberance 44 on the punch 34 forms the central concavity 46 in the preform 20 and the annular peripheral portion 48 of the punch 34 forms the flat annular top portion 50 of the top surface 60 of the briquette 20.

At the same time, the core rod 40 forms a socket 52 in the tapered neck 54 of the briquette 20 below the lower conical side 56 thereof, while the side portion 32 of the die cavity 24 forms a side surface 58 thereon extending downward from the top surface 60. Concurrently therewith, the annular bottom surface 62 of the briquette 20 is formed by the annular top surface 64 of the tubular lower punch 36.

When the briquetting stroke of the upper punch 34 has been completed, the upper punch 34 is retracted upward out of the die cavity 24. The lower punch 36 is then caused to move upward upon an ejection stroke so as to eject the preform 20 from the mold cavity 24. The foregoing operations are repeated until a suitable number of the preforms 20 has been made in this manner, whereupon they are mounted upon a block 68 (FIG. 2) of suitable temperature-resistant material, such as ceramic or refractory material. The assembly is then transferred to a conventional sintering oven where sintering is performed in a suitable protective atmosphere, such as dissociated ammonia, at an elevated temperature for a satisfactory period of time. In a successful practice of the invention, a temperature of 2,090" F. for a period of 2% hours, employed because of the oxide content of the water-atomized powder, which inhibits good sintering.

Meanwhile, a valve stem 70 has been prepared from a suitable material, such as ordinary suitable carbon steel, for example that steel known inthe steel industry as SAE 8150 steel, upon which a slightly flared reduced-diameter nose portion 72 has been formed by cold heading or by automatic screw machine operation. The flared nose portion 72 may be characterized as having a reverse taper in that the upper end 74 is of a slightly larger diameter than the lower end 76, leaving an annular marginal shoulder 78 between the nose portion 72 and the shank 80 of the valve stem 70.

The valve stem 70 is then dropped into the lower bore 82 (FIG. 3) of the die cavity 84 of a hot-forming die 86 mounted in a conventional hot-forming press (not shown). The die cavity 84, as before, includes an upper cylindrical portion 88, an upper intermediate shallow conical portion 90, and a lower more sharply tapered or conical surface 92 opening at its lower end into the lower bore 82. The valve stem 70 is so positioned in the lower bore 82 that the nose 72 projects upward into the cylindrical portion 88 of the die cavity 84. A trumpetshaped or funnel-shaped sleeve 95 approximately fivethousandths of an inch in thickness of a suitable lubricant metal (FIG. 5), such as copper, is then dropped into the die cavity 84 over the nose portion 72 of the valve stem 70, with its lower end coming to rest upon the annular outer upper surface 78 thereof.

The preform 20, reheated to a temperature of approximately 2,350 F. for about 5 minutes in an endothermic atmosphere, is then dropped into the die cavity 84 within the copper sleeve 95, and with the socket 52 fitting over the nose portion 72 of the stem 70 in telescoping relationship therewith.

The upper punch 94 of the hot-forming press (FIG. 4) is then caused to descend into the die cavity 84 which it snugly but slidably fits, exerting a pressure of approximately tons per square inch in a single blow. Thereupon, the central convex protuberance 96 and the annular flat peripheral surface 98 on the lower end 100 of the punch 94 form corresponding concave and flat surfaces 102 and 104 respectively on the upper surface 106 of the top portion 108 of the now formed valve head 110, while the side rim surface 112 acquires the configuration of the adjacent surface 88 of the die cavity 84. At the same time, the compressive force exerted by the upper punch 94 densities and thins the sintered powdered metal in the preform 20 to form the top portion of the valve head 110.

Meanwhile, the neck portion 54 of the briquette 20 and the nose portion 72 of the valve stem 70 are extruded downward, along with the lubricant metal sleeve 95 into the lower portion 92 of the die cavity 84, elongating these portions to form the elongated neck portion 114 interlocked with the elongated nose portion 116 of the valve stem 70, and at the same time forming a layer 118 of nonferrous lubricant metal on the outer surface of the neck portion 114. The upper punch 94 is then retracted upward, whereupon an ejector plunger or punch (not shown) ejects the now semifinished valve, generally designated 120. After being allowed to cool sufficiently for handling, the semifmished valve 120 is subjected to further grinding and finishing operations, together with the optional formation of multiple annular grooves by conventional turning and grinding operations, where such grooves are called for.

When several samples of the thus formed semiiinished valve were cut longitudinally (FIG. 4), it was found that the flared nose portion 72 of the valve stem 70 between its opposite ends had become stretched by the hot-forming operation so as to have acquired a narrowed intermediate part of concavely arcuate longitudinal section while the socket 52 of the neck 54 of the briquette between its opposite ends had acquired a correspondingly bulged intermediate part of convexly arcuate longitudinal section interfitted and interlocked therewith,

The formation of the valve head blank of the composite hightemperature-resistant valve- 10 from so-called gasatomized superalloy powder (FIGS. 6 to 9 inclusive) follows a somewhat different procedure because of the fact that the gasatomized particles are substantially smooth and round, hence do not naturally interlock with one another as do the wateratomized particles, as described in connection with FIGS. 1 to 5 inclusive. A graphite block mold 130 is prepared with multiple mold cavities 132 -(FIGS,6 and 7), each having a shape similar to that of the briquetting die cavity 24 of FIG. 1.The mold 130 directly beneath the cavities 132 is provided with bottom recesses 134 with which each mold cavity 132 communicates by way of a vertical bore 136. Seated in the bore 136 is the shank 138 of a core pin 140, also of graphite, and having a head 142 disposed in its recess 134 and also having a slightly tapered upper end urtion 144 projecting upward into the mold cavity 132.

The mold cavities 132 are filled with a charge of the gasatomized metal powder compacted without the heavy briquetting compression to which the water-atomized particles of the briquette 20 of FIGS 1, 2 and 3 were subjected. The thus-charged block mold 130 is then transferred to a sintering furnace and sintered at a similar temperature and for a similar period of time in a similar protective atmosphere to that described above. The mold 130 is then removed from the furnace and the preforms 146 ejected from the mold cavities 132, leaving the preforms 146 with slightly tapered sockets 148 in the neck portions 150 thereof and with head portions 152 conforming to the shapes of the mold cavities 132,

A valve stem 70 is then dropped into the lower bore 82 leading to the die cavity 84 of a hot-forming die 86 similar to that described in connection with FIGS. 3 and 4, the same reference numerals being henceforth applied to corresponding parts. A trumpet-shaped lubrication sleeve 95 of nonferrous metal (F165) is then dropped into the die cavity 84 surrounding the nose portion 72 of the valve stem 70. The nose portion 72 is slightly flared, as before. A preform 146, either while still hot from the sintering furnace or reheated to a similar temperature, is then dro ped into the die cavity 84 with its tapered socket 148 exten mg downward over the nose portion 72,The upper punch 94 of the hot-forming press containing the die 86 is then caused to descend into the die cavity 84 (FIG. 9), compressing and densifying the head portion 152 and at the same time causing it to conform to the shape of the die cavity 84 while the central convex protuberance 96 and the annular flat peripheral surface 98 on the lower end 100 of the upper punch 94 form the corresponding concave and flat surfaces 102 and 104 respectively on the upper surface 106 of the now formed valve head 110. At the same time, the side rim surface 112 acquires the configuration of the adjacent surface 88 of the die cavity 84 Whilc this is occurring, as the upper punch 94 descends it densities and thins the sintered owdered metal in the head portion 152 of the preform 146 to form the top portion 108 of the valve head 110.

Simultaneously with the compression, densification and formation of the top portion 108 of the valve head 110, the neck portion 150 of the preform 146 and the nose portion 72 of the valve stem 70 are forced downward, together with the lubricant metal sleeve 95 into the lower portion 92, elongating these portions and at the same time interlocking them, to form the elongated neck portion 114 interlocked with the elongated nose portion 116 of the valve stem 70, and at the same time forming a thin layer 118 of nonferrous lubricant metal on the outer surface of the neck portion 114 of the valve head 110. The upper punch 94 is now retracted upward, whereupon an electroplunger or punch (not shown) ejects the now semifmished valve, generally designated 120.As before, the semifinished valve 120 is subsequently subjected to further grinding and finishing operations, together with the optional formation of multiple annular grooves 15 by conventional turning and grinding operations where such grooves are called for.

lclaim:

1. A composite high-temperature-resistant valve, comprismg:

a valve stem of carbon steel having a shank with a reduced diameter nose portion thereon and with a shoulder extending therearound between said shank and said nose portion; and

an enlarged valve head of high-temperature-resistant sintered powdered alloy metal having a higher melting point than said stem extending over the end of said nose portion in completely covering protective relationship therewith and having a neck portion with its rearward end disposed adjacent said shoulder and with a socket therein disposed in tightly gripping mating engagement with said nose portron, said nose portion between its forward end and said shoulder having a narrowed intermediate part of smaller diameter than said forward end, and said socket between its opposite ends having a correspondingly narrowed intermediate part of smaller diameter than the forward end of said socket matingly interlocked with said intermediate part of said nose portion.

2. A composite high-temperature-resistant valve, according to claim 1, wherein the inner end of said nose portion is of bulbous shape within said socket.

3. A composite high-temperature-resistant valve, according to claim 1, wherein said head has an exposed layer of nonferrous metal disposed on the exterior of said neck portion beneath said head. 

2. A composite high-temperature-resistant valve, according to claim 1, wherein the inner end of said nose portion is of bulbous shape within said socket.
 3. A composite high-temperature-resistant valve, according to claim 1, wherein said head has an exposed layer of nonferrous metal disposed on the exterior of said neck portion beneath said head. 